A variety of snowmobile ski suspension systems have been employed on snowmobiles over the years. In the early 1980's the assignee of the present invention introduced to the snowmobiling industry an independent front suspension system utilizing a trailing arm-i.e., an elongated arm having its front end connected to the steering spindle, and the rear end pivotably connected to the chassis (see, e.g., Canadian Pat. No. 1,227,823. The trailing arm is oriented generally parallel to the snowmobile's longitudinal centerline and generally parallel to the ground. The pivotal connection of the rear end of the trailing arm to the chassis is provided to permit the front end of the arm to move upwardly and downwardly as the ski encounters uneven terrain.
Under certain operating conditions snowmobile riders sometimes wish to adjust the performance characteristics of the front suspension system. For example, sometimes an operator will choose to use a shock/spring setup which permits less vertical travel of the front suspension. This modification can change the "at rest" or "normal" position of the front end of the trailing arm, and, therefore, cause a corresponding change in the caster of the ski spindle (which turns within the cylindrical sleeve carried at the front end of the trailing arm).
The caster of the ski spindle is significant, affecting both the performance of the front suspension and steering effort required. The ability of the suspension to efficiently absorb perturbances as the ski encounters moguls, bumps, etc. is increased as the caster angle is increased (i.e., as the top end of the ski spindle is tipped rearward), but steering effort is also increased-steering effort is reduced by making the ski spindle more vertical, but this sacrifices some of the performance of the suspension.
Thus, it would be desirable to permit a user to adjust the caster of the ski spindle when making other adjustments to the suspension system. The assignee of the present invention previously sold a limited production run of snowmobiles having two discreet mounting points for the rear end of the trailing arm. While permitting some adjustment of caster, the system required disconnection of the rear end of the trailing arm and provided only one alternative position for the trailing arm.